Automatic telephone-exchange system



Oct. 20, 1925. 1,557,993

A. H. DYSON AUTOMATIC TELEPHOIiE EXCHANGE SYSTEM Filed July 12 11Sheets-Sheet .1

Oct. 20, 1925. 1,557,993

A. H. DYSON AUTOMATIC TELEPHONE EXCHANGE SYSTEM Filed July 12, 1906 11sheets sha'et 2 Oct. 20,1925. f v A 1,557,993

A. H. DYSON AUTOMATIC TELEPHONEEXCHANGE SYSTEI Filed July 12, 1906 11Sheets-Sheet 5 Oct; 20, 1925. 1,557,993

A. H. DYSON AUTOMATIC TELEPHONE EXCHANGE SYSTEI Filed Ju1y 12, 1906Sheets-Shoot 4 Oct. 20,1925. 1.557593 A. H. DYSON AUTOMATIC TELEPHONEEXCHANGE SYSTEM Filed Jul 12, 1906 11 Sheets-Sheet 5 Oct. 20,19251.557.9 3

A. H. DYSON AUTOMATIC TELEPHONE EXCHANGE SYSTEM Filed July 12 1906 11Sheets-Sheet 6 Oct. 20, 1925.

A. H. DYSON AUTOMATIC TELEPHONE EXCHANGE SYSTEI Filed-Julylz, 1906 11Sheets-Shoot '7 A. H. DYSON AUTOMATIC TELEPHONE EXCHANGE SYSTEM Oct. 20,1925- 1906 11 Sheets-$11661. 8

Filed July 12 Oct. 20, 1925.

1,557,993 A. H. DYSON AUTOMATIC TELEPHONE EXCHANGE SYSTEI 11Sfiets-Sheet 9 Filed July 12 1906 Oct. 20, 1925. 1,557,993

- A. H. DYSON AUTOMATIC TELEPHONE EXCHANGE SYSTEM Filed July 12, 1906 11Sheets-Sheet 10 Oct. 20, 1925. 1,557,993

, A. H. DYSQN AUTOMATIC TELEPHONE EXCHANGE SYSTEM Filed July 12 1906 11Sheets-Sheet 11 till Patented Oct. 20, 1925.

UNITED STATES ALFRED H. DYSON, or CHICAGO, ILLrnoIs, A-ssIe NoR, BYMESNE KELLOGG SW ITCHBOARD &

1,557,992; PATENT orrics.

ASSIGNMENTS, TO

SUPPLY 00., A CORPORATION OF ILLINOIS;

AUTOMATIC TELEPHONE-EXCHANGE SYSTEM.

Application filed July 12, 1906. Serial No. 325,830.

To all whom it may concern.

Be it known that I, ALFRED H. DYSON, a citizen of the United States, andresident of Chicago, county of Cook, and State of Illinois, haveinvented new and useful Improvements in Automatic Telephone-ExchangeSystems, of which the following is a specification.

My invention relates more particularly to a structure including theprovision of party line service in connection with automatictelephonesystems, but is in no sense limited by any such party line features. Ihave illustrated my invention in such a system employing a plurality ofswitches successively operated for completing each connection betweencallin subscribers lines and e called subscribers lmes.

As is well known, in commercial automatic systems of this character,subscribers lines are ordinarily'divided into groups of one hundred,each group having their line terminals multipled to bank'contacts 01,say, ten connectors each of which is capable of connecting with any lineof the hundred group. The calling subscriber, by appro-' priatemechanism controlled from his substation, selects the group ofconnectors wanted, and, after a connector of that group has beenautomatically individualized to his line, operates the same to completethe de-' sired. connection. Thus in an exchange of ten thousandsubscribers lines, there would be one hundred groups of one hundredlines, each group having its appropriate less numerous group ofconnectors. tion of ten connectors to one hundred lines is arbitrary.

For clearness of illustration, I shall assume my invention to beemployed in an exchange of ten. thousand subscribers, sup

plied with four party line service. There would thus be twenty-fivehundred individual lines, each having four stations connect-- ed'to it.j-- I For commercially satisfactory party line service, non-interferingselective, ringing is required, and one system of this character (thatdisclosed in patent to Wm. W Dean,

No. 779,533, dated January 10, 1905-, title, Party line telephonesystem) I shall refer to as employed in connection with my invention,though other systems may readily be employed.

This system operates upon the well-known The proporv1050. After theconclusion of principle of tuned bells responding separately to ringingcurrents of different pre determined frequency.

' In the system I have assumed, the ten thousand party line subscriberswould be divided into groups of one hundred subscribers each and aparticular group of connectors would be assigned to each group ofsubscribers. Each one hundred line group would include subscribers onlywhose substationbells respond to one particular frequency of ringingcurrent.

Subscribers lines would still be arranged in groups of one hundred eachhaving their terminals multipled to connector banks. Instead, however,of having one group of connectors capable of making connection withthem, there would be four such groups of ten connectors each, the lineterminals being multipled to forty connector contact banks. Each of thefour groups of connectors have their ringing apparatus connected to aringing machine of a different frequency, and current is projected overa called line of the frequency appropriate for ringing the bell of thesubstation wanted, without ringing the other bells on the line Ingeneral terms, for party line service, each groupoi one hundredsubscribers is represented at the exchange by its own individual groupof connectors, just as in single line systems; In making a call forsubscriber 1050, whose number is in the group 1000l100, for instance,the calling subscriber wouldselect and employ a connector of the groupappropriated to those numbers 10001100 and operate it to connect withline 50 of the line group. Ringing current of frequency #1, we will say,is now projected over the called line and rings bell the conversation,the lines are disconnected and the calling subscriber makes asecond'call. Assume the wanted subscriber is number 1150 in the group1100-1200. This may be considered a substation on the same line as 1050just before called; The calling subscriber selects and employsa'connector of the group assigned to subscribers 1100-l200. Thisconnector willhave access to terminals of the same lines as thatemplo'yedi't'or connecting to 1050, and will be brought to connect withline 500i the same line group, i e., the same line. But this connectorof group 1l00-1200 be projected over the called line and bell No. 1150is now rung.

Having indicated in a general way the arrangement of apparatus employedn carrying out my invention, I will'nojv mention some of the problemsmore particularly involved in the provision of such serv ce.

As is well known, it is necessary, in order to prevent existingconversations from be ing interfered with, to arrange the structure ofan automatic telephone system so that when lines are busy, othersubscribers shall fail in endeavors to get into communication with them.Furthermore, a calling line is made to test busy soon after a call isindicated. This is moreover especially desirable in party line service,since, were it not so, while party A of a line is making his call, partyB might be called up by some one else and the line taken away from A.

From these considerations arise the problem of enabling a callingsubscriber to, connect a selected connector to his own line and ring outover that line to call a substation on the same line, withoutsacrificing the preferred method of operation whereby a calling line ismade busy soon after a call is initiated, and held so until the callingor called subscriber releases it. In accordance with my invention, Iprovide mechanism for rendering the calling line busy after a subscriberinitiates a call, and mechanism including means operated wheneverconnection is made with a called line, whether the same or another, formomentarily (and only so) removing the test potential from the connectorbank contacts of the calling line. Thus in calling ones own line, theline will test idle at the moment the connector is to complete itscircuit, while a call from any other line will find the line busy unlessit chances to make co-incident; connection, a circumstance ofnecessarily rare occurence.

The ordinary practice has been in automatic telephone systems to releaseor destroy an existing connection by simultaneous grounding er thesubstation line limbs, accompli hed whenever the substation receiver isreplaced on the hook, This will not do for party line service inasmuchas during a coniersation, a n -d1 party on either one or the connectedlines,'whe might desire to make call and so remove his receiver, would,on hearing conversation proceeding, replaceh'js receiver,t-herebygrounding the two line limbs and disconnectingthe lines. Toprevent this, I have arranged the structure of my invention in suchmanner that release is accomplished, after connection has been made,only when one of the connected lines has its circuit conductivelybroken, the arrangement being such that; when the circuit of either oneof a connected line pair is opened, all switches employed in theconnection are restored,

Until a connection is actually completed, however, the replacing of areceiver at any substation on a line will, by grounding the line limbs,release the switches. Thus no subscriber can, after partially making acall, leave his receiver off the hook and prevent other subscribers onhis line from restoring the common apparatus to normal.

The general ob'ect of my invention is to provide an efficient and simplestructure for supplying party line service in automatic telephonesystems of the described character, embodying the advantages andcombinations more particularly pointed out in the specific descriptionsof the drawings and in the claims.

In the drawings, I have elected to illustrate my invention incombination with common battery automatic telephone systems, whichsystems, as well as the party line structures, are of my invention. Ishall describe the party line system in connection with three suchsystems, differing principally in the manner whereby a first selector isbrought into operative relation with the calling substations, it beingunderstood that, in either system, are first selectors individual totelephone lines employed.

The first of these systems is one wherein each subscribers line isprovided with a simple switch individual to it, operated on the removalof a substation receiver to select an indifferent idle first selectorand place it under control of the telephone line.

The second system differs from the first in that no switches individualto subscribers lines are used. In this second system, first selectorsare assigned, in groups of ten, to one hundred subscribers lines, whichselectors are in permanent association, each with its own auxiliaryswitch, which I shall call a line selector. In accordance with thissecond system, when asubscriber at a calling substation removes hisreceiver, he operates a mechanism common to the group of one hundredlines among which hislinc is included, which starts an idl line selectorin search of bank contacts ofdiis line, which appear in association withthe line selector wipers. The line selector seeks these contacts cut andgagenrent with them, thereby placing an idle first selector in operativerelation with the calling substation line Salient features of myinvention, common to both systems, are the employment or a single pairofrelays adapted for operation by directive currents transmitted fromthe substation, which relays control tl e operatlng magnets of the firstselector, second selector and connector successively, thus doing awaywith relays for each switch. Another feature common to the two systemsis a structure employed "for releasing the switches employed in theconnection, its arrangement its wipers come to rest in en- (Lil beingsuch that the release of all switches employed in a connection isaccomplished when either subscriber of two connected lines replaces hisreceiver.

My invention includes also certain novel arrangements of substationcalling apparatus arranged for employment in connection with the centraloffice systems. As will be understood from the description of these, atime interval is required between the initial substation switchingoperation to cause the placing of a first selector in connection with acalling line and the time when the first set of directive switchingimpulses is to be sent and the calling device is especially arranged tosecure such interval.

Referring to the drawings, Fig. 1 shows diagrammatically circuitsembodying my invention; Fig. 2 shows a varying circuit structure; Fig. 3shows a plan view of a line selector bank; Fig. at shows a modificationof the structure of Fig. 2; Figs. 5, 6 and 7 show side and front viewsof line selector mechanism; Figs. 8, 9 and 10 show similar views of aconnector mechanism; Fig. 11 is a sectional view of a line selector;Figs. 12 and 13 illustrate release and special switch mechanism of afirst selector; Fig. 14 shows detail of a primary off-normal switch;Fig. 15 illustrates the special ringing mechanism of a connector; Fig.16 winding mechanism thereof; Fig. 17 is starting mechanism; and Fig. 18its circuit changing combination; Fig. 19 shows the circuit changingmechanism of special releasing mechanism for a first selector; Figs. 20and 21 show front and side views of a private sw1 ch; Figs. 22 and 23show slmilar views of a master switch;

Fig 2a is a front view of the calling device; r ig. 25 is a rear viewthereof; Fig. 26 shows special governor mechanism for the device; Fig.2? is a top view of the calling device; Fig. 28 is a view thereof on thesectional line indicated in Fig. 27; Fig. 29 shows the governor of thecalling device; Fig. the friction member thereof; and Fig. 31 thereceptacle of said member.

In Fig. 1, four substations A, B, C and D are indicated, station A beingdiagrammatically shown in full, B, C and D being indicated only by theirbranch conductors from limbs P and S. These are connected by the linelimbs P and S with the private switch E at the exchange; Each substationincludes the usual condenser and call-bell normally held in bridge oflimbs P and S by hook lever A, the latter being adapted, on removal ofthe receiver, to place the bell in open circuit and connect thetransmitter in metallic circuit with the line. The calling device 1 isprovided, diagrammatically shown as a disk with teeth of insulatingmaterial, capable of clockwise rotation by the hand of the subscriberand adapted, when thereafter released, to be returned by the as sociatedspring, its insulated teeth then operating upon spring 2 to connect limbP of the line to ground G intermittently a number of times,corresponding to the extent of rotation and the number of teeth therebybrougat beneath spring 2. After the last tooth of dial 1 has passedabove 2, a tooth at the left of the dial closes momentarily limb S toground C by operating spring 3, in its return t dial is in other thannormal position, the pin thereon moving with it allows spring 1 by itstension to disengage spring 1', whereby limbs P and S are temporarilydisunited during the substation switching operations. An arm 5, fastenedto hook lever 1, moves over the top of spring 6 when the receiver isremoved; and upon the subsequent replacing thereof, presses spring 6 toa position where it is connected with the two associate springs; andground G is thereby temporarily applied to both line limbs P and S. Asthe hoolclever descends to normal, arm 5 passes over the top of spring 6which then disengages its associate springs. Substations B, C and D haveeach equipment identical with that of A, as have also substations A, B,C and D at the right of Fig. l.

The exchange apparatus of Fig. 1 includes the private switch E,individual to the calling line and capable, when a call is initiated, ofbringing an indifferent idle first selector under control of the callingline. The lines may conveniently be divided into groups of one hundredlines each, each line being provided with its private switch includingthe wipers 21, 24.- and 27, adapted to engage multipled terminals of anappro priate number of first selectors, say ten. A first selectorcircuit is shown at F. Its passive terminals 23, 26 and 29 are shown asmultipled a single time, but it will be understood that they would infact be multipled one hundred times, once to each private switch of theone hundred lines the selector is to serve.

There would be associated with wipers 21, 24 and 27, nine additionalsets of contacts 28, 26 and 29, each leading to a difierent firstselector.

The principal function of a first selector in a ten thousand line systemis to respond to the thousands digit impulses transmit-- ted from thesubstation and move its wipers under their influence to a group ofcontacts associated with them and tiplicd terminals of longing to avlimited group of subscribers, one thousand in number. As 'we havesupposed an exchange of ten thousand subscribers, the wipers 63, 64: and65 of first selector F would have accessible to them ten such groups ofsecond selector terminals, one for eachone thousand subscribers in theexchange. The number 0 normal as shown. When the forming mulsecondselectors be of second selectors for each thousand group, appearing bytheir terminals at a first selector, is ordinarily ten, and a firstselector contact bank may therefore comprise one hundred second selectorterminals arranged in ten groups of ten each.

The group of second selectors of the appropriate one thousand havingbeen selected, wipers 63, 64 and are caused to move over the terminalsof the group, passing by terminals of busy switches and stopping inengagement with terminals of the first idle second selector.

The terminal contacts 78, 79 and 80 of second selector G are shownmultipled a single time, but it is to be understood that they would inpractice he multipled to a large number of first selectors, say onehundred.

The function of the second selector G is to respond to the hundredsdigit impulses transmitted from the substation and move its wipers undertheir influence to an associated group of contacts forming ter1ninals ofconnectors belonging to a particular limited group of subscribers, onehundred in number. As a second selector is assigned to a particular onethousand subscribers, it has accessible to its wipers ten groups ofconnector terminals, one group for each one hundred subscribers of itsthousand. A group of second selector bank contacts will ordinarilyinclude terminals of ten connectors.

I have shown terminals 91, 93 and 95 of a connector H in Fig. 1 asmultiplied a single time, but it will be understood that they will infact be mutiplied to a large number of second selectors, ordinarily onehundred times.

The function of a connector H is to respond to the tens and units digitimpulses transmitted from the substation and move its wipers under theinfluence of the tens digit impulses to a group of ten line terminalsamong which the line of the wanted subscriber is included, andthereafter under influence of the units digit impulses move the wipersinto engagement with the terminals of the particular line with which thewanted subscribers substation is con nected.

The terminals 7, 8 and 9, shownat circuit I in Fig. 1, would in the fourparty line selective ringing system of my invention ordinarily bemulti'ple'd to the contact banks of forty connectors, which, asindicated in the general statement of my invention, would be dividedinto four groups, the switches of each group connecting with the sameone hundred sets of line terminals, but the connectors of each of thefour groups being arranged to supply ringing current of a differentfrequency to whatever line one of them may be connected. to, for thepurpose of ringing selectively the bell of one of the four substationson the line.

As the circuit features are the principal part of my invention, themechanical features being subordinate thereto, 1 shall first describeFig. 1; and for purposes of illustration, I shall assume that subscriberA desires to enter into conversation with subscriber D whose number is2345 and whose bell is tuned to respond to current of frequency #4.

It is to be understood that all apparatus in Fig. 1 is shown at normal.

Subscriber A first removes his receiver, hook-lever 4 engaging itsopposed contact and conductively uniting the line limbs P and S. Thiscauses relay 13 to attract its armatures, circuit being traced fromground G through normal wiper contact 2524, upper armature of relay 15,over limb P, through hook-lever 4, returning over limb S, lower armatureof relay 15, normal wiper contact 27-28, winding of relay 13 to bat tery130.

The attracted left-hand armature of relay 13 is now connected to groundG and has closed circuit from said ground via right armature of relay17, through vibratory magnet 14 to battery 130. Magnet 14 is therebyactuated and effects a forward offnorinal step of wipers 21, 24 and 27,the former, 21,, engaging permanently grounded contact 22 andestablishing a locking path for current through the now attractedrightarmature of relay 18, the relay winding and to battery. Vipers 24and 27 advance upon contacts 25 and 28 without disengaging them, readyto be moved to engage the first set of first selector contacts 23, 26,29, on a second actuation of magnet 14.

The first movement of the wipers also caused off-normal switch springs10 and 11 to disengage one another and to make contact with theirrespective opposed contacts. Spring 12 is also shifted to engage itsalternate contact. The movement of spring 11 connects G with themultiple contacts 7 at the connector banks, alternating their potentialto render them buy, while the movements of springs 10 and 12 completecircuit from G through relay 15 to battery, which relay, by attractingits arm'aturels, disconnects wipers 24 and 27 from limbs P and S so thatthe said wipers are in open circuit while passing over contacts 26, 29,of busy first selectors, in order to prevent interference with existingconversations.

Relay 13 continuing energized, magnet 14 vibrates its armature a secondtime, which moves Wipers 21, 24 and 27 to engage contacts 28, 26 and-29of the first selector of the group. If this switch is idle, contact 23is in the condition shown, insulated from ground. Viper 21 having leftcontact 22 and engaged open contact 28, circuit is broken through relay13, Whose retracted left armtaure opens the circuit of magnet 14,preventing further actuation thereof and hence further movement of thewipers. The retracted left armature of relay 13 also causes relay 15 tobe (ls-energized, whose armatures thereupon connect Wipers 24 and 27with line limbs P and S.

The retracted right armature of relay 13 has now connected ground Gthrough release magnet 16 with wiper 21 and contact 23 and all itsmultiples, to render the first selector busy.

Thus if it is supposed that a second private switch such as E is startedby the removal of the receiver at its substation, wiper 21 of suchswitch, upon leaving its contact 22 to engage a multiple of contact 23of Fig. 1, will find said contact grounded through magnet 16 at Gr ofthe private switch of A. Circuit will therefore be continued throughrelay 13 of this second private switch, its magnet 14 will again vibrateits armature, moving wipers 21, 24, 27 along to engage terminals 23, 26,29 of the next first selector, when wiper 21 again tests the switch andthe foregoing is repeated till an idle set of selector terminals isreached.

Release manget 16 is of relatively low efliciency and when placed inseries with relay 13 of another private switch, as just described, doesnot attract its armatures, al though said relay l3 continues energized.

Subscriber A now operates dial 1 to transmit two current impulses fromG, through spring 2, over limb P, upper armature of relay 15, contact 21-26, spring 30, its normal contact, upper armature of relay 3 1,through primary relay PR to battery. The twice attracted armature of PRcauses t'ansmission of two current impulses from ground, through springcontact 5150, switch spring 55, primary magnet PM to battery. PM isthereby twice actuated and moves wipers 63, 6 1., 65 two steps to pro):-imity with a group of contacts such as 78, 79 and 80,"terminals ofsecond selectors belonging to the second thousand group of subscribers.

lVith t 1e first primary step of wipers 63, 64-, 65, primary off-normalswitch spring 57 engages its opposed contact, while spring is shifted toits alternate position.

Following the two impulses over limb P, a single impulse is transmittedfrom G, through spring 3, over limb S, traversing the lower armature ofrelay 15, contact 2729, spring 32 and its normal contact, lower armatureof relay 34;, the winding of secondary relay SE to battery. Themomentarily attracted armature of SR closes contacts 5152 and 5354. Theclosure of the latter completes a circuit from ground at switch E,through right winding of relay 17, right armature of relay 13,

contacts 2123, 5354 and to battery through resistance 35. Release magnet16 at E is in a branch extending to this circuit, but due to itssluggi-shness and the presence of resistance 35, does not attract itsarmatures at this time. The 'armatures of relay 17 are attractedmomentarily,armature 18' temporarily removing the busy groundfromcontact 7. Each time secondary relay SR is actuated by an impulsetransmitted from the substation, this process is repeated. Thus for.four momentary periods during the establishment of a connection, oncefollowing the transmission of each set of digit impulses, a calling linehas its guarding potential temporarily removed.

Returing now to the operation of switch F, the temporary closure ofcontact 5152 causes a current impulse from ground through said contact,spring 56, busy relay BR to battery 130. BR attracts its armatures,whereof 60, engaging its opposed contact, completes a circuit fromground G through spring 57, spring 58 and its opposed contact, armature60 and its opposed contact, through secondary magnet SM to battery 130.SM being provided with a vibratory circuit attracts and releases itsarmature, moving wipers 63, 64. and (now on open circuit at contacts 59and 62) to engage contacts 78, 79 and 80, terminals of the first secondselector of the previously selectedgroup. If this switch is idle, thencontact 78 is on open circuit, as shown at G, busy relay BR losescurrent, and armature 60 falls back to prevent a second actuation ofsecondary magnet SM and hence further movement of the wipers. The otherarmatures also fall back, whereof 60 places G7 in connection with wiper63 and contact 78 and its multiples, via spring 57 and spring 58 and thelatters opposed contact, to render the second selector busy.

W'ith the first (and in this case, the only) actuation of SM, secondaryoff-normal switch springs 55 and 56 are moved to disengage their normalcontacts, cutting the primary magnet PM and the busy relay BR out ofoperative relation with the primary and secondary relays PR and SR.

Supposing,now, that a second first selector F is brought to engagemultiples of contacts 78, 79 and 80. Viper 63 of this second switch willfind ground from G of the selector Fig. 1 thereon; its busy relay BRwill be locked by current from ground Gr of Fig. 1, to wiper 63 of thesecond switch, via the right armature of its release ma net RM and itsnormal contact; armature 61 and its opposed contact through BR tobattery. All armatures of the busy relay of this second switch willtherefore remain attracted, armature 60 continuing the vibratory circuitof secondary magnet SM'of this other switch, which will advance itswipers 63, 64., 65, to engage the next contacts of the group of secondselector terminals. If this switch is idle, the busy relay will bedemagnetized and the wipers arrested. If busy, however, another lockingcircuit will be established through the busy relay, its armatures willremain attracted, and successive vibrations of the armature of thesecondary magnet will occur till wiper 63 reaches an idle terminal, whencir cuit through the busy relay of the second switch willbe broken andits armatures retracted.

Returning now to the calling subscriber at A, he next operates his dialto transmit from G, over limb P, current impulses corresponding innumber to the hundreds digit of the called subscriber. These threeimpulses trave1se the winding of primary relay PR, following the beforetraced path. Three attractions and releases of the armature of PRtransmit three impulses from ground through contact 51-50, armature 59and its contact (contact 55 is now open), through (Mr-79 contact 82, theprimary magnet PM of the second selector G to battery 131. Magnet PM,responsive to these three impulses, causes three movements of wipers.90, 92, 9 1, to bring them to proximity to a group of ten setsof'contacts 91, 93, 95, terminals of ten connectors, which connectorsare provided with one hundred sets of bank contacts forming terminals oflines to which telephone substations of the two thousand three hundredgroup areconnected. The ringing connections of these connectors are allalike and extend from a ringing generator of such frequency as tobe'capable of ringingthe bells of the one hundred substations numberedas above, only, the bells of such substations being properly attuned torespond to generator currents of this frequency, while the bells ofother substations that may be connected to the same lines, will beincapable of responding to the particular frequency of the generatorconnected to said connectors.

The first actuation of PM at G also caused off-normal switch springs 81and 88 to be shifted toengage their associate. contacts, while spring 89is also shifted.

An impulse over limb S from G, following the third impulse over P,energizes secondary relay SR, and an impulse flows from ground, throughcontact 5152, contact 62, contact 80, contact 83, the busy relay BR at Gto battery 131.

The busy relay BB is thereby energized and attracts its armatures, theattactio'n of completing circuit from ground, through spring 88, spring89 and its opposed contact, attracted armature 85, through secondarymagnet SM to battery. The resulting energization of SM moves wipers 90,92 and 94 to engage contacts 91, 93 and 95, forming terminals of thefirst connector of the selected group. If this connector is idle, asshown at H, contact 91 is on open circuit; and at the cessation of theimpulse through BR, the relay is de-energized and its armaturesretracted. The retraction of 85 opens circuit through secondary magnetSM, pre venting further vibration of its armature, whereby wipers 90, 92and 94 are left in engagement with contacts 91, 93 and 95 of H. Thearmature 85, in engaging its normal contact, connects ground Gr throughsprings 88 and 89, the armature 85 and the rightarmature of releasemagnet RM tocontact 91 and its multiples, rendering the connector busy.The first actuation of SM also actuates secondary ofi-normal switchsprings 82 and 83 to disengage their associated contacts, thus cuttingthe'primary magnet and the busy relay out of operative. relation withcontacts79 and 80. i

Supposing now that a second second-selector similar to G brings itswipers to engage multiples of contacts 91, 93 and 95. In such case,wiper of this second switch will find ground G connected to the multipleof contact 91 engaged by it; a locking path for the busy relay BR of thesecond switch will therefore be established via its wiper 90, itsarmature 86, through the busy relay to battery. The busy relay of thissecond switch will therefore continue to hold its armature 85 attractedand its secondary magnet SM will continue in circuit, vibrating itsarmature a second. time to move the wipers90, 92 and 94: of this secondswitch to engage a set of contacts forming terminals of a secondconnector of the group. If this is busy, a locking path similar to thatjust described will be produced for ER, and the secondary magnet SM ofthe second switch will continue vibratingits armature until its wipers90, 92 and 9 t. reach terminals of an idle connector.

Subscriber A new transmits four impulses from ground G, over limb P,through primary relay PR, the four resulting actuations of said relaytransmitting four current impulses from ground through contact 5150,contact 59, contact 04 79, contact 84:, contact 92-93, spring 90 at connector H, armature 98, primary magnet PM to battery, causing fouractuations of PMF. These actuations are effective to move wipers 124:,126 and 127 of the connector to a position adjacent to a group ofcontact sets in the connector bank, forming terminals of lines 11, 1-2,43. etc. to 19 followed by 40, of the one hundred line group to whichthe wipers have access. It will be remembered that forty substations areconnected to these ten lines. With the first of the four primarymovements of the wipers, off-normal switch spring 10% engages itsassociated contact.

The single impulse over limb S, following the four impulses over limb P,causes secondary relay SR to transmit an impulse of current from ground,through contact 5152, contact 62, contact 80, contacts 87, 91-95,through spring 97 and its normal contact, contact 100, secondary magnetSi to battery. The resulting actuation of SM causes wipers 124., 126 and127 to ad: Vance step toward the group of connector bank contactsselected. The normal position of these wipers with respect to the edgeof the contact bank is such that two steps are required to bring them toengage the first contact set of a selected group. This first actuationof SM? caused secondary off-normal switch spring 96 to be shifted intoengagement with its opposed contact, while spring 97 is shifted todisengage its normal contact, but not to an extent to bring it intoengagement with its opposed contact, this engagement occurring only withthe second energization of Sly .1 The purpose of this delay is toprevent a possible actuation of test relay TR, which might otherwise bemomentarily ctuated by the impulse now being transmitted from sec ondaryrelay SR if the operation of 97 were rapid enough to engage its opposedcontact before the impulse ended. Such an unintended energization of TRwould cause the attraction and release of its armature, effecting theshifting of spring 103, controlled by the said relay, which .would causethe calling subscriber to be connected with the line he now proceeds toselect, Whether said line were busy or not, as will be apparent from thedescription of the testing operation hereinafter made.

Subscriber A new transmits five impulses from G, over limb P, throughrelay PR, Which in turn transmits five impulses over the previouslytraced path, through contact 92-93, the current now flowing throughspring 96 and its opposed contact, through armature 105 and its normalcontact, secondary magnet SM to battery. Five resulting actuations ofthe secondary magnet are effective to move wipers 124, 126 and 127successively into engagement with the first, second, third, fourth andfifth contact sets of the selected group. The last of these is a setforming terminals of the line to which the telephone of the wantedsubscriber #2345 is connected.

A single impulse, flowing over limb S at the conclusion of the last ofthe five impulses over limb P, by energizing the secondary relay SR,causes an impulse to be transmitted over the previously traced path toand through contact 9495, thence by spring 97 and its opposed contact,through armature 108 and its normal contact, the left winding of testrelay TR to battery. The test relay attracts its annatures.

Assuming first that the called line is idle, which is' the conditionillustrated at I of Fig. 1, contact 7 is connected to battery 131,through armature 18, spring 12 and the winding of relay 15. Armature 101has connected the right winding of the test rclay tothe same pole ofbattery 131 and hence no locking path for the said relay TR exists; andon the cessation of the inipulse transmitted through its left winding,the relay TR is Clo-energized, its armatures 101 and 102 falling back.The de-energization of the relay TB is also effective to throw spring103 to engage its alternate contact, whereupon current flows from groundG through relay 105, energizing the said relay, spring 103 and itsopposed contact, contact 12 1- 7, armature 18, spring 12, relay 15 tobattery, energizing also relay 15, whose attracted armatures disconnectthe called line from the private switch and connect it to the terminalcontacts 8 and 9,.

now engaged by wipers 126 and 127.

The connection of ground G by the shifting of spring 103, through wiper124 to contact 7 and its multiples, has placed the called line in suchcondition that if it be now supposed that wiper 124.- of anotherconnector is brought to engage contact 7, the ensuing energization ofthe'test relay of this other connector, by an impulse transmitted overlimb S of the other calling line, will cause the test relay to be lockedby a current flowing over a path that may be traced as follows: fromground G of the connector, Fig. 1, through its relay 105, its shiftedspring 103, its wiper 124, through contact 7, thence to a multiple ofsaid contact engaged by the Wiper 12a of the other connector now seekingconnection with the called line, through the unshifted spring 103 ofthis other connector, through attracted armature 101" of its test relayTR to battery. This flow prevents the de-energization of the test relayon the cessation of the impulse through its left winding, its armature102 continues attracted, and the busy signal is transmitted from machine132 through armature 102, through spring 97 of the other connector andthence through the talking-circuit of the secondselector and thefirst-selector, there traversing condenser 133, through the receiver atthe calling substation and back over limb P to battery,'notifying thesubscriber that the line wanted is busy, whereupon he replaces hisreceiver and the apparatus he has used in attempting connection with thebusy line is restored to normal, as hereinafter explained.

Returning now to the point where subscriberA brought the connectorwipers to rest engaging contacts 7, 8, 9, of the line of D, the currentflowing through relay 105 caused its armatures to be attracted. A

7 ground first result of this is the closing, by armatures 105 and 108,of two normally open contacts in the talking circuit about to beestablished. Armature 105 also connects 11 through contact 99, contact106105", spring 96 and to the left via the upper talking conductor,through contact 59 at F, contact 50- 19, spring 31 and relay 3-1 tobattery. Relay 34 is thereby actuated to bridge the battery 130 acrossthe line of A via the windings of relay 36. The latter is therefore inturn actuated and its armatures are attracted, whereof 38 and 39 connectthe relays windings with the calling line via springs and 13, whilearmature 40 completes circuit "from ground, through the armature ofrelay 16, to battery, actuating said relay. This re lay, on itssubsequent de-energization, eti ected at the proper time as hereafterexplained, releases the switches.

Returning to relay 105 at H, a further etl ect of its actuation at thistime, caused by the attraction of armature 109, is the closure ofcircuit from ground, through said armature 109, spring 113 and magnet116 of ringing device M to battery, energizing 116, a branch path ofsaid circuit being also established through relay 115 energizing it.

The apparatus at M includes the notched disk 117 pivoted at its center,having fastened to it the circular rack 117 and cam 117". Toothedarmature 118 of magnet 116 normally engages rack 117, holding the diskfrom rotation. Power is provided for the disk so that it continuallyency to rotate in the direction of the arrow.

Magnet 116 having become energized as above described, armature 118 isattracted,

disk 117 is released and commences rota-' tion', spring120 immediatelyrising to ride upon the periphery of 117 and engaging spring 121,whereby ringing current of frequency #4, the same being. adapted to ringthe bell at station D, is projected from the common generator 123,through contact 121120, the attracted upper armature of relay 115,contact 126-8, the attracted upper armature of relay 15, over limb P,through the bells of the substations of the line in parallel, returningover limb S, the lower attracted armature of relay 15, contact 9 127,the lower attracted armature ofrelay 115 and through the circuits ofbattery 131. As disk 117 completes a revolution, spring 120 rides downinto a first notch to disengage spring 121. An instant later, it ridesdown into a second. and deeper notch in which position it closes contact120122.

Assuming that at this time subscriber D, whose bell. alone was rung, hasanswered the call by removing his receiver. Instantly circuit iscompleted from ground G through the lower winding of relay 111,

through contact 122-120, upper armature release relay RR has a tendofrelay 115, out over limb P, over the conductive path now established bythe raised hook-lever at substation D, returning over limb S, the lowerarmature of 115 to battery. This current causes relay 111 to attract itsarmatures, 111 and 11 1 closingnormally open contacts in the connectortalking conductors, while armature 112 contacts with spring 113 to lockits relay 111 by means of its upper winding and thereafter open thecircuits of magnet 116 and relay 115, which become de-energized.

All this occurs instantly and while spring 120 continues in the deepnotch of 117. The armature of magnet 116 would now be retracted, but isfor a moment prevented by the detent ot' pivoted arm 119. This arm dropsdown oil from the raised portion ot cam 117 when disk 1.17 is firstmoved, and its pawl then engages armature 118, holding it againstretraction.

hen now, under the present circumstances, disk 117 reaches the point ofcomplete rotation (which it immediatel i does), arm 119 is lifted by cam117 to release armature 118, which flies back and, engaging rack 117stops the disk in the position shown, wherein spring 120 is in anintermediate position.

As soon as armatures 111 and 111 engage their associate contact-s, asbefore described, battery 131 was placed in bridge or" the line limbs Pand S of subscriber D, through the windings of relay 110. The attractedarmature of 110 opens the circuit before traced from ground Gthrough relay 3 1, which relay is tie-energized, its armaturesretracted, and springs 30, 81,-and 32, 33, are shifted to engage theiropposed contacts. The shifting of springs 30"and 32 disconnect thewindings of relays PR and SR and complete the talking circuit of firstselector F. The shifting of spring 33 completes circuit from ground,through relay d1 to battery, and the armatures of said relay firstengage springs 13 and 415 and then cause said springs to disengage theirnormal contacts. By this actuation of relay 11, the direction of theflow of current from battery 130 in the line of calling subscriber A isreversed.

The subscribers A and D are now in corn versation, the talking circuitbeing traced from station A to D, through the exchange by way of theheavily marked conductors, battery being fed to the line of A throughthe windings of relay 36 from 130, and to the line of D through thewindings of relay 110 from battery 131.

The condensers c and c are in the two talking conductors at theconnector and, owing to their presence, there is no flow of directcurrent through the windings of the relay 16. This relay isdifferentially wound, so as to ofier no material impedance to therapidly alternating voice currents. The left lill whose retractedarmature connects grouiul G through contact 99, contact 106105 spring 96via the upper talking conductor to the left, the left-hand winding ofrelay 46, spring 30 and its opposed contact, contact 4-3-4-2, armature39 and the lower winding of relay 36 to battery 130. Relay 16 attractsits armature,lopening circuit through release relay RE (which has beenenergized during conversation). Onits vde=energization, RR by itsretracted armature eil'ects a thrust of pawl 66, and the said pawlhaving, on the energization of RR, been brought to engage a tooth o'titsassociated rack adjacent to that shown en 'aeed b I it disk 67 isrotated one step so that spring 68 rests on the periphery of 67, inwhich position it engages its associate contact, closing circuit fromground, through spring .68 and magnet 69 to battery. Magnet 69, armature70 and arm T1 of apparatus L have the same mechanical tunetions withrespect to disk 72, its rack and cam, that magnet 116 at H, armature.118

and arm 119 have to disk 11?.

As reagent 69 is now energized, disk 72 is allowed to rotate.Immediately after its start, spring 73 engages 7st, closing circuitthrough'relay RR from ground, via spring 68 and contact 7374 to battery,again ener'gizing ER. Spring 73 then rides upon the periphery, openingcontact 73-71, and RR becomes de-energized, pawl 66 causing disk 67to'advance a second stepwhenspring 68 engages a tooth of 67 and istherefore at normal. The movement of spring 68 de-energizes magnet 69,but disk 72 completes its rotation because of the interlock between 71and '70, only broken at the completion ota revolution when its breakingwill cause disk 72 to be arrested at its normal position.

As disk 72 starts on its rotation, spring v76 rides to the periphery,closing contact 75-76. Circuit is thereby closed tt'romG at switch E,through release magnet 1(3,"-retracted armature of relay l3,contact21-23, terminal of spring 54, contact 76-75, release magnet RM tobattery. As magnet 16 and magnet RM are both of low resistance, thebranch circuit through the right winding of relay 17 is not edective, byits shunting effeet, to prevent the attraction of the armatures ofmagnet 16, and release magnets 16 and RM are both fully actuated.

The attraction of the right armature of RM completes circuit throughrelease niagnet RM. at switch "G, the cnergiaation of RM in turncompleting circuit through re lease magnet RM at the connector H. Thedescribed ene-rgizations of the tour release magnets prepare theirrespective switch mechanism for their returns to normal as soon as themagnet shall become de-energized.

In addition to the mechanical efl'ects produced, described hereafter inconnection with the 'n'iechanical drawings, circuit changes are producedby each release magnet to disconnect its switchs wipers ant place themon open circuit while being re stored, so that their necessary wipingover busy contacts may not interfere with other connections.

Magnet 16 at switch E, when energized, shifts spring 132 to engage itsnormal contact. Spring 11, being an cit-normal switch spring, is notrestored till switch E reaches normal. Hence spring '12 completes thecircuit of relay 15, whose attracted armatures hold wipers 2 1 and 27 onopen circuit durin the release.

RM a switch F. when energized, shifts spring 58 to nor1nal,'and,off-normal spring 5? remaining temporarily connected to (i clay BB isenergized and disconnects wipers and 65, pending restoration.

tiiiniiarly, RM shiftsspring 89 to energize BR.

.fit connector H,1nagnet RM when energized, shifts spring 103 to normalwhich opens the circuit of relay 105, whose retracted armature 109causes relay 111 to be de-energized, whose armatures are retracted. 111and 114 disconnecting wipers 126 and 127.

Returning now to apparatus L at switch 1", the above operations are allperformed in a very brief space of time and before disk 72 completes arevolution. 1V hen a revolution is completed, contact 75-76 is opened asshown, and release magnets 16 and RH are (lo-energized, the formerrestoring switch in; the latter restoring switch F, its retractedarmature also shifting springs 30, 31, and 32, to normal. i Ioreover,the de-energization of RM opens circuit through RM, restoring the secondselector (1 The de-energization of RM opens circuit through RM whichthereuponrestores the connector H. and all apparatus is then at normal.

If subscriber A replaces his receiver in advance of subscriber D,circuit is opened through relay 36 at first selector F, whose armature40 opens the circuit of relay RR and'the release operations proceed asbefore.

It will be remembered that springs and 32 are shifted from their normalpositions only on the response at the called substation. Relays PR andSRtherefore remain in circuit with the ailing line up to that time.Subscriber A, it he tails to ecure a re- 1's,;'. 1 SPODSQ (2P'cllzillgCS 111; 11111111 lit-cl 111i lllf:

